The present invention is drawn to a process and a device for extruding tubes or similar hollow sections from a billet wherein the billet is forced by an extrusion stem against a die, in particular against a multi-chamber die with welding zone, wherein the die surrounds a mandrel on a mandrel support.
There are multi-chamber dies with welding zone in which the entry orifices are positioned around the mandrel which determines the shape of the interior of the hollow section produced. The mandrel is mounted on a system of struts in the die which form a mandrel support and must withstand very large forces which increase with a corresponding increase in the cross section or size or circumscribing circle. Such a system suffers from a number of disadvantages, in particular when manufacturing large tubes which frequently leads to fracturing of the mandrel support.
Accordingly, it is the principal object of the present invention to provide an improved process and device for extruding hollow sections in which, during the extrusion operation, there is less load on the mandrel support and consequently an increase in the lifetime of the extrusion tool under optimum use of the extrusion force.
Further objects and advantages of the present invention will appear hereinbelow.